Sound reproduction is a balancing act of many characteristics or features of the sound. Conventional sound recordings are mastered at a reference sound level that is rarely reproduced in a users listening environment. Sound reproduced at levels different than the reference level suffers from differences in one or more characteristics such as tonal balance that may degrade the listening experience.
Conventional sound processing devices may include one or more user controls such as a loudness button. This button tends to enable a fixed set of filters that tend to boost bass, or boost bass and treble. Conventional solutions: a) do not vary continuously with the volume control and, b) cannot apply an accurate equal loudness correction since the difference between the current playback level and the reference level is unknown.